Light emitting device and method for manufacturing the same

ABSTRACT

Disclosed are a light emitting device and a method for manufacturing the same. A light emitting diode comprises a plurality of Un-GaN layers and a plurality of N-type semiconductor layers, an active layer on the N-type semiconductor layer, and a P-type semiconductor layer on the active layer, wherein at least two of the Un-GaN layers and at least two of the N-type semiconductor layers are alternatively stacked on each other.

The present application claims priority under 35 U.S.C. 119 and 35U.S.C. 365 to Korean Patent Application No. 10-2007-0039534 (filed onApr. 23, 2007), which is hereby incorporated by reference in itsentirety.

BACKGROUND

The embodiment relates to a light emitting diode and a method formanufacturing the same.

A light emitting diode is formed by sequentially stacking a bufferlayer, an unintentionally doped GaN layer (Un-GaN layer), an N-type GaNlayer, an active layer, and a P-type GaN layer on a substrate.

The light emitting diode has a characteristic in which electrons areinserted into holes on the active layer to emit light if power isapplied to the N-type GaN layer and the P-type GaN layer.

Meanwhile, since the substrate has a lattice constant different fromthat of the N-type GaN layer, dislocation may occur, and the bufferlayer and the Un-GaN layer reduce a difference between lattice constantsof the substrate and the GaN layer.

However, the buffer layer and the Un-GaN layer have a limitation in thereduction of the difference of the lattice constants, and thedislocation density may be increased due to the Un-GaN layer.

SUMMARY

The embodiment provides a light emitting device and a method formanufacturing the same.

The embodiment provides a light emitting device and a method formanufacturing the same, capable of reducing dislocation density.

The embodiment provides a light emitting device and a method formanufacturing the same, capable of reducing lattice mismatching, therebyimproving a light emitting characteristic.

According to the embodiment, a light emitting device comprises aplurality of Un-GaN layers and a plurality of N-type semiconductorlayers, an active layer on the N-type semiconductor layer, and a P-typesemiconductor layer on the active layer, wherein at least two of theUn-GaN layers and at least two of the N type semiconductor layers arealternatively stacked on each other.

According to the embodiment, a method for manufacturing a light emittingdevice, comprises the steps of alternatively forming a plurality ofUn-GaN layers and a plurality of N-type semiconductor layers on asubstrate, forming an active layer on the N-type semiconductor layer,and forming a P-type semiconductor layer on the active layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view used to explain a light emitting diode according to thefirst embodiment; and

FIG. 2 is a view used to explain a light emitting diode according to thesecond embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description of the embodiments, when layers (films), regions,patterns, or elements are described in that they are formed on or undersubstrates, layers (films), regions, or patterns, it means that they areformed directly or indirectly on or under the substrates, layers(films), regions, or patterns.

The thickness and size of each layer shown in the drawings can besimplified or exaggerated for the purpose of convenience or clarity. Inaddition, the elements may have sizes different from those shown indrawings in practice.

Hereinafter, a light emitting diode and a method for manufacturing thesame with reference to accompanying drawings.

FIG. 1 is a view used to explain a light emitting diode according to afirst embodiment.

The light emitting diode according to the first embodiment comprises asubstrate 10, a buffer layer 20, a first Un-GaN layer 31, a first N-typeGaN layer 32, a second Un-GaN layer 33, a second N-type GaN layer 34, anactive layer 40, a P-type GaN layer 50, and an ohmic electrode layer 60.A first electrode layer 70 is formed on the second N-type GaN layer 34,and a second electrode layer 80 is formed on the ohmic electrode layer60.

As shown in FIG. 1, the light emitting diode according to the firstembodiment includes the first and second Un GaN layers 31 and 33 and thefirst and second N-type GaN layers 32 and 34, which are alternativelyand repeatedly stacked on the buffer layer 20.

As shown in FIG. 1, the Un-GaN layer and the N-type GaN layer arerepeated twice.

According to the first embodiment, the first N-type GaN layer 32 isformed between the first and second Un-GaN layers 31 and 33, therebypreventing the occurrence of a dislocation density due to the first andsecond Un-GaN layers 31 and 33. According to the first embodiment, aplurality of Un-GaN layers are provided, in which each Un-GaN layer isthinner than an Un-GaN layer provided in a single layer structure of theUn-GaN layer and an N-type GaN layer according to the related art.Similarly, each N-type GaN layer may be thin a conventional N-type GaNlayer.

In other words, the increase of dislocation density occurring as theUn-GaN layer becomes thick is prevented by forming a plurality of thinUn-GaN layers.

For example, the first and second Un-GaN layer 31 and 33 may havethicknesses in the range of 0.5 μm to 1 μm, and the first and secondN-type GaN layers 32 and 34 may have thicknesses in the range of 1 μm to1.5 μm.

According to the first embodiment, the dislocation density of the firstand second N-type GaN layers 32 and 34 is reduced as the N-type GaNlayers become close to the active layer 40, that is, distant from thebuffer layer 20.

To this end, the first and second Un-GaN layers 31 and 33 and the firstand second N-type GaN layers 32 and 34 are formed in a chamber having ahigher temperature and a lower pressure while reducing the amount ofTMGa flowed into the chamber as the Un GaN layers and the N-type GaNlayers are close to the active layer 40.

Further, since a dislocation density may be increased as theconcentration of impurities is increased in the first and second N-typeGaN layers 32 and 34, the concentration of N type impurities isdecreased as the N-type GaN layers become close to the active layer 40.

FIG. 2 is a view used to explain a light emitting diode according to asecond embodiment.

The light emitting diode according to the second embodiment comprises asubstrate 10, a buffer layer 20, a first Un-GaN layer 31, a first N-typeGaN layer 32, a second Un-GaN layer 33, a second N-type GaN layer 34, athird Un-GaN layer 35, a third N-type GaN layer 36, an active layer 40,a P-type GaN layer 50, and an ohmic electrode layer 60. A firstelectrode layer 70 is formed on the third N-type GaN layer 36, and asecond electrode layer 80 is formed on the ohmic electrode layer 60.

As shown in FIG. 2, the light emitting diode according to the secondembodiment has the first, second, and third Un-Ga layers 31, 33, and 35and the first, second, and third N-type GaN layers 32, 34, and 36alternatively stacked on the buffer layer 20.

As shown in FIG. 2, the Un-GaN layers and the N-type GaN layers arerepeated three times.

Although it is not shown, the Un-GaN layers and the N-type GaN layersmay be repeated four times according to another embodiment.

According to the second embodiment, the first and second N-type GaNlayers 32 and 34 are alternately provided in relation to the first,second, and third Un-GaN layers 31, 33, and 35, thereby preventing theincrease of dislocation density by the first, second, and third Un-GaNlayers 31, 33, and 35. According to the second embodiment, a pluralityof Un-GaN layers are provided. In this case, the first, second, andthird Un-GaN layers 31, 33, and 35 are thinner than an Un-GaN layerprovided in a single layer structure of the Un-GaN layer and an N-typeGaN layer according to the related art. Similarly, the first, second,and third N-type GaN layers 32, 34, and 36 may be thin a conventionalN-type GaN layer.

In other words, the increase of dislocation density occurring as theUn-GaN layer becomes thick is prevented by forming a plurality of thinUn-GaN layers.

For example, the first, second, and third Un GaN layers 31, 33, and 35may have thicknesses in the range of 0.3 μm to 0.6 μm, and the first,second, and third N-type GaN layers 32, 34, and 36 may have thicknessesin the range of 0.5 μm to 1μ.

According to the second embodiment, the dislocation density of theN-type GaN layer is reduced as the N-type GaN layer becomes close to theactive layer 40, that is, distant from the buffer layer 20.

To this end, the Un-GaN layer and the N-type GaN layer are formed in achamber having a higher temperature and a lower pressure while reducingan amount of TMGa flowed into the chamber as the Un-GaN layer and theN-type GaN layer are close to the active layer 40.

Further, since a dislocation density may be increased as theconcentration of impurities is increased in the first, second, and thirdN-type GaN layers 32, 34, and 36, the concentration of N-type impuritiesis decreased as the N-type GaN layers become close to the active layer40.

As described above, in the light emitting diode according to theembodiments, a plurality of thin Un-GaN layers are provided, and theN-type GaN layers are provided between the Un-GaN layers in order toprevent the increase of dislocation density caused by the Un-GaN layers.Accordingly, the increase of the dislocation density in the Un-GaN layercan be prevented due to the N-type GaN layer.

In addition, the light emitting diode according to the embodiments isprovided such that dislocation density is decreased as the N-type GaNlayer becomes close to the active layer 40.

Accordingly, the dislocation density of the N-type GaN layer in contactwith the active layer 40 is decreased so that the light emittingcharacteristic of the light emitting diode can be improved.

Hereinafter, a method for manufacturing the light emitting diodeaccording to the embodiment will be described in detail with referenceto FIG. 2.

The buffer layer 20 is formed on the substrate 10. For example, thesubstrate 10 includes at least one of Al₂O₃, Si, SiC, GaAs, ZnO, andMgO.

The buffer layer 20 is used to reduce a difference between latticeconstants of the substrate 10 and the GaN layer stacked on the substrate10. For example, the buffer layer 20 may have a stacking structure suchas AlInN/GaN, In_(x)Ga_(1-x)N/GaN, orAl_(x)In_(y)Ga_(1-x-y)N/In_(x)Ga_(1-x)N/GaN.

For example, the buffer layer 20 may be grown by flowing TMGa and TMInat a flow rate of 3×10⁵ Mol/min into the chamber, in which the substrate10 is positioned, and flowing TMA1 at a flow rate of 3×10⁶ Mol/min intothe chamber together with hydrogen gas and ammonia gases.

The first Un-GaN layer 31, the first N-type GaN layer 32, the secondUn-GaN layer 33, the second N-type GaN layer 34, the third Un-GaN layer35, the third N-type GaN layer 36 are sequentially formed on the bufferlayer 20. The first, second, and third Un-GaN layers 31, 33, and 35 andthe first, second, and third N-type GaN layer 32, 34, and 36 may beformed through a metal-organic vapor chemical deposition (MOCVD)process.

First, the first Un-GaN layer 31 is formed on the buffer layer 20. Forexample, the first Un-GaN layer 31 may be formed by flowing NH₃(3.7×10⁻² Mol/min) and TMGa (2.9×10⁻⁴-3.1×10⁻⁴Mol/min) gas in a state inwhich the chamber is adjusted to have internal pressure of 500 Torr to700 Torr and the internal temperature in the range of 1040□ to 1050□.

Then, the first N-type GaN layer 32 is formed on the first Un-GaN layer31. For example, the first N-type GaN layer 32 is formed by flowing NH₃(3.7×10⁻² Mol/min), TMGa (2.9×10⁻⁴-1×10⁻⁴ Mol/min), a SiH₄ gas includingN-type impurities such as Si in a state in which a chamber is adjustedto have an internal pressure of 500 Torr to 700 Torr and an internaltemperature the temperature in the range of 1040□ to 1050□.

In this case, the first N-type GaN layer 32 may have a dislocationdensity of 10¹⁰/cm¹ or less. In addition, Si may be implanted into thefirst N-type GaN layer 32 with the concentration of 7×10¹⁸/cm².

The second Un-GaN layer 33 is formed on the first N-type GaN layer 32.The second Un-GaN layer 33 is formed by flowing a less amount of TMGagas in a chamber with a lower pressure under a higher temperature ascompared with the process of performing the first Un-GaN layer 31.

For example, the second Un-GaN layer 33 may be formed by flowing NH₃(3.7×10⁻² Mol/min) and TMGa (1.9×10⁻⁴-2.1×10⁻⁴ Mol/min) gas in a statein which a chamber is adjusted to have an internal pressure of 300 Torrto 500 Torr and an internal temperature in the range 1050° C. to 1060°C.

The second N-type GaN layer 34 is formed on the second Un-GaN layer 33.The second N-type GaN layer 34 is formed by flowing a less amount of aTMGa gas and an SiH₄ gas in a chamber with a lower pressure under ahigher temperature as compared with the process of performing the firstN-type GaN layer 32.

For example, the second N-type GaN layer 34 may be formed by flowing NH₃(3.7×10⁻² Mol/min), TMGa (1.9×10⁻⁴-2.1×10⁻⁴ Mol/min), and a SiH₄ gasincluding N-type impurities such as Si in a state in which a chamber isadjusted to have an internal pressure of 300 Torr to 500 Torr and aninternal in the range of 1050

to 1060

.

In this case, the second N-type GaN layer 34 may have the dislocationdensity of 10⁹/cm³ or less. In addition, Si may be implanted into thesecond N type GaN layer 34 with the concentration of 5×10¹⁸/cm².

The third Un-Gan layer 35 is formed on the second N-type GaN layer 34.The third Un GaN layer 35 is formed by flowing a less amount of a TMGagas in a chamber with a lower pressure under a higher temperature ascompared with the process of performing the second Un-GaN layer 33.

For example, the third Un-GaN layer 35 may be formed by flowing NH₃(3.7×10⁻² Mol/min) and TMGa (1.4×10⁻⁴-1.6×10⁻⁴ Mol/min) gas in a statein which a chamber is adjusted to have an internal pressure of 200 Torrto 300 Torr and an internal temperature in the range of 1060° C. to1070° C.

The third N-type GaN layer 36 is formed on the third Un-GaN layer 35.The third N-type GaN layer 36 is formed by flowing a less amount of aTMGa gas and an SiH₄ gas in a chamber with a lower pressure under ahigher temperature as compared with the process of performing the secondN-type GaN layer 34.

For example, the third N-type GaN layer 36 may be formed by flowing NH₃(3.7×10⁻² Mol/min), TMGa (1.4×10⁻⁴-1.6×10⁻⁴ Mol/min), and a SiH₄ gasincluding N-type impurities such as Si in a state in which a chamber isadjusted to have an internal pressure of 200 Torr to 300 Torr and aninternal temperature in the range of 1060° C. to 1070° C.

In this case, the third N-type GaN layer 36 may have the dislocationdensity of 10⁸/cm³ or less. In addition, Si may be implanted into thethird N-type GaN layer 36 with the concentration of 3×10¹⁸/cm².

The active layer 40 is formed on the third N-type GaN layer 36. Forexample, the active layer 40 may have a multi-quantum well structureincluding InGaN/GaN which is grown at a nitrogen gas atmosphere byflowing TMGa and TMIn into the chamber.

The P-type GaN layer 50 is formed on the active layer 40. For example,the P-type GaN layer 50 may be grown by supplying TMGa (7×10⁻⁶ Mol/min),TMAl(2.6×10⁻⁵ Mol/min), (EtCp₂Mg) (Mg(C₂H₅C₅H₄)₂) (5.2×10⁻⁷ Mol/min),and NH₃(2.2×10⁻¹ Mol/min using hydrogen as a carrier gas.

The ohmic electrode layer 60 is formed on the P-type GaN layer 50. Forexample, the ohmic electrode layer 60 includes at least one of ITO, CTO,SnO₂, ZnO, RuO_(x), TiO_(x), IrO_(x), and Ga_(x)O_(x).

After the above stacking structure is formed, a mask layer (not shown)is formed on the ohmic electrode 60. The ohmic electrode layer 60, theP-type GaN layer 50, the active layer 40, and the third N-type GaN layer36 are selectively etched so that a portion of the third N-type GaNlayer 36 is exposed upward.

The first electrode layer 70 is formed on the third N-type GaN layer 36,and the second electrode layer 80 is formed on the ohmic electrode layer60.

Accordingly, the light emitting diode according to the embodiments canbe manufactured.

In the light emitting diode and the method for manufacturing the sameaccording to the embodiments, the Un-GaN layer and the N-type GaN layerare alternatively stacked, thereby reducing the dislocation density onthe N-type GaN layer adjacent to the active layer.

Further, in the light emitting diode and the method for manufacturingthe same according to the embodiments, a plurality of Un-GaN layers andN-type GaN layers are provided. In this case, the Un-GaN layers and theN-type GaN layers are formed by reducing an amount of TMGa flowed intothe chamber while increasing the temperature of a chamber and reducingthe pressure of the chamber step by step. Accordingly, the dislocationdensity of the N-type GaN layer adjacent to the active layer may be morereduced.

In the light emitting diode and the method for manufacturing the sameaccording to the embodiments, a plurality of Un-GaN layers and aplurality of N-type GaN are formed. In this case, the N-type GaN layeris formed by reducing an amount of N-type impurities step by step.Accordingly, the dislocation density of the N-type GaN layer adjacent tothe active layer can be more reduced.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A light emitting device, comprising: a plurality of undoped GaNlayers and a plurality of N-type semiconductor layers; an active layeron an upper layer of the plurality of N-type semiconductor layers; and aP-type semiconductor layer on the active layer, wherein at least one ofthe undoped GaN layers and at least one of the N-type semiconductorlayers are alternatively stacked on each other.
 2. The light emittingdevice as claimed in claim 1, wherein the plurality of undoped GaNlayers and the plurality of N-type semiconductor layers comprise asequence of layers including a first undoped GaN layer, a first N-typesemiconductor layer, a second undoped GaN layer, and a second N-typesemiconductor layer.
 3. The light emitting device as claimed in claim 1,wherein the undoped GaN layers and the N-type semiconductor layerscomprise a sequence of layers including a first undoped GaN layer, afirst N-type semiconductor layer, a second undoped GaN layer, a secondN-type semiconductor layer, a third undoped GaN layer, and a thirdN-type semiconductor layer.
 4. The light emitting device as claimed inclaim 1, wherein the P-type semiconductor layer is directly on theactive layer.
 5. The light emitting device as claimed in claim 1,wherein the plurality of N-type semiconductor layers comprise Si.
 6. Thelight emitting device as claimed in claim 2, wherein the first andsecond N-type semiconductor layers comprise GaN, and wherein the secondN-type semiconductor layer comprise at least two layers.
 7. The lightemitting device as claimed in claim 2, wherein the second N-typesemiconductor layer has a dislocation density lower than a dislocationdensity of the first N-type semiconductor layer.
 8. The light emittingdevice as claimed in claim 2, wherein the second N-type semiconductorlayer has an impurity concentration lower than an impurity concentrationof the first N-type semiconductor layer.
 9. The light emitting device asclaimed in claim 2, wherein the first and second undoped GaN layers havea thickness in a range of 0.5 μm to 1 μm.
 10. The light emitting deviceas claimed in claim 2, wherein the first and second N-type semiconductorlayers have a thickness in a range of 1 μm to 1.5 μm.
 11. The lightemitting device as claimed in claim 3, wherein the first, second, andthird N-type semiconductor layers comprise GaN.
 12. The light emittingdevice as claimed in claim 3, wherein the second N-type semiconductorlayer has a dislocation density lower than a dislocation density of thefirst N-type semiconductor layer, and wherein the third N-typesemiconductor layer has a dislocation density lower than a dislocationdensity of the second N-type semiconductor layers.
 13. The lightemitting device as claimed in claim 3, wherein the second N-typesemiconductor layer has an impurity concentration lower than an impurityconcentration of the first N-type semiconductor layer, and wherein thethird N-type semiconductor layer has an impurity concentration lowerthan an impurity concentration of the second N-type semiconductor layer.14. The light emitting device as claimed in claim 3, wherein the first,second, and third undoped GaN layers have a thickness in a range of 0.3μm to 0.6 μm.
 15. The light emitting device as claimed in claim 3,wherein the first, second, and third N-type GaN layers have a thicknessin a range of 0.5 μm to 1 μm.
 16. A method for manufacturing a lightemitting device, the method comprising the steps of: alternativelyforming a plurality of undoped-GaN layers and a plurality of N-typesemiconductor layers on a substrate; forming an active layer on theN-type semiconductor layer; and forming a P-type semiconductor layer onthe active layer, wherein the undoped-GaN layers and the N-typesemiconductor layers are formed by stacking a first undoped-GaN layer, afirst N-type semiconductor layer, a second undoped-GaN layer, and asecond N-type semiconductor layer, and wherein the second undoped-GaNlayer and the second N-type semiconductor layer are formed by flowing asmaller amount of TMGa into a chamber having a higher temperature and alower pressure as compared with a condition for manufacturing the firstundoped-GaN layer and the first N-type semiconductor layer.
 17. Themethod as claimed in claim 16, wherein the second N-type semiconductorlayer has an impurity concentration lower than an impurity concentrationof the first N-type semiconductor layer.
 18. A method for manufacturinga light emitting device, the method comprising the steps of:alternatively forming a plurality of undoped-GaN layers and a pluralityof N-type semiconductor layers on a substrate; forming an active layeron the N-type semiconductor layer; and forming a P-type semiconductorlayer on the active layer, wherein the undoped-GaN layers and the N-typesemiconductor layers are formed by stacking a first undoped-GaN layer, afirst N-type semiconductor layer, a second undoped-GaN layer, a secondN-type semiconductor layer, a third undoped-GaN layer, and a thirdN-type semiconductor layer, wherein the second undoped-GaN layer and thesecond N-type semiconductor layer are formed by flowing a smaller amountof TMGa into a chamber having a higher temperature and a lower pressureas compared with a condition for manufacturing the first undoped-GaNlayer and the first N-type semiconductor layer, and the thirdundoped-GaN layer and the third N-type semiconductor layer are formed byflowing a smaller amount of TMGa into a chamber having a highertemperature and a lower pressure as compared with a condition formanufacturing the second undoped-GaN layer and the second N-typesemiconductor layer.
 19. The method as claimed in claim 18, whereinimpurities implanted into the second N-type semiconductor layer are lessthan impurities implanted into the first N-type semiconductor layer, andimpurities implanted into the third N-type semiconductor layer are lessthan impurities implanted into the second N-type semiconductor layer.20. A light emitting device, comprising: a plurality of first GaN-basedsemiconductor layers alternatively stacked with a plurality of secondGaN-based semiconductor layers; an active layer on the plurality offirst GaN-based semiconductor layers alternatively stacked with theplurality of second GaN-based semiconductor layers; and a P-typesemiconductor layer on the active layer, wherein each of the pluralityof first GaN-based semiconductor layers has a level of doping lower thana level of doping of any one of the plurality of second GaN-basedsemiconductor layers.
 21. The light emitting device as claimed in claim20, wherein the plurality of first GaN-based semiconductor layersinclude at least one undoped GaN-based semiconductor layer.
 22. Thelight emitting device as claimed in claim 20, wherein the plurality offirst GaN-based semiconductor layers and the plurality of secondGaN-based semiconductor layers each include two layers.
 23. The lightemitting device as claimed in claim 20, wherein the plurality of firstGaN-based semiconductor layers and the plurality of second GaN-basedsemiconductor layers each include three layers.
 24. The light emittingdevice as claimed in claim 20, wherein the plurality of first GaN-basedsemiconductor layers and the plurality of second GaN-based semiconductorlayers each include more than two layers.
 25. The light emitting deviceas claimed in claim 20, wherein the active layer is on an uppermostlayer of the plurality of first GaN-based semiconductor layers.
 26. Thelight emitting device as claimed in claim 20, wherein the active layeris on an uppermost layer of the plurality of second GaN-basedsemiconductor layers.
 27. The light emitting device as claimed in claim20, wherein the active layer is directly on the plurality of firstGaN-based semiconductor layers alternatively stacked with the pluralityof second GaN-based semiconductor layers.
 28. The light emitting deviceas claimed in claim 20, wherein the P-type semiconductor layer isdirectly on the active layer.
 29. The light emitting device as claimedin claim 20, wherein the plurality of second GaN-based semiconductorlayers include N-type semiconductor layers comprising Si.